Yes they are. The 8 3/4 is 56.5", and the 7 1/4 is 57.X". If you don't believe me and want to call BS, break out a tape measure and see for yourself.

http://www.moparts.org/Tech/Archive/axle/17.html

That is such a crap statement. Im no expert, and I have never broken a 7 1/4.My 67 Dart GT was my daily driver,20,000 miles a year in So. Cal traffic,and I beat the crap out of it.Stock,2bbl,head work,4bbl,headers. It wasnt untill I changed the stall and cam that I swapped it out,and only then I did it so I would have better gear/LSD options. Now that same rear is running around So Cal still in a buddys 66 Valiant daily driver.


As for using the 9" rear drums with front discs I've done it(did it with the above mentioned 67 dart),and know many others that have as well with no issue. What exactly makes it foolish?

While I know the 8 3/4 is different, the link says the 8 3/4 is the same 57 1/8 as the 7 1/4. Not sure what dimension A is in the chart, but there is not an 1.8 inch difference in width between them.

From my own experience, my tires rubbed slightly on the outer wheel wells with the 7 1/4 if I had stuff in the trunk. But after I installed an 8 3/4 they have never touched.

Check the link again,look at the flange to flange measurements.

I have, moparts is wrong.

While I do agree that moparts is wrong,the 7 1/4 is wider that the 8 3/4. Like I said before its about an inch difference.

Dimension "A" in the chart at Moparts is the measurement from housing flange to housing flange (where the backing plate bolts on), not from axle flange to axle flange.

From the Mopar Performance/ Direct Connection Chassis book.
7 1/4 "A" body standard track=55.56 inches
67-72, 8 3/4 "A" body standard track=55.6 inches.
So all this argument is about .040 inches.

So now can everyone calm down? Please!

PS: while looking this up I learned something else, on 7 1/4 rear gears
4.10 ratio P4007001
4.30 ratio P4007002
4.50 ratio P4007003
4.80 ratio P4007004
5.10 ratio P4007005
5.30 ratio P4007006
I was not aware of this many ratios.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

not worried about the width issue( I thought they were the same?), but I had no idea there were that many gear ratios! (if you could find them)
Thanks for posting Charlie!

the 10" drum on a 7 1/4" is not only a slightly longer shoe,but it's also wider too?

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1964 Dart GT

The BBP 7.25" is about an inch or so wider than a SBP one because of the B body brakes they used on them. The SBP 7.25" should be the same as a SBP 8.75"

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Official Cookie and Mater Tormentor.

New Question: If I wanted to Upgrade the rear brakes(on 1964 Dart)so I ended up with 10" drums and BBP, what car am I looking for ?

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1964 Dart GT

I dont mean to argue this. I am just speaking from my experience with the matter. When I swapped my 7 1/4 out for an 8 3/4, it was about an inch wider and I had a noticeable difference in handleing characteristics. The 7 1/4 seemed a little better balanced,especially when going around a corner.

I like better balance! I'm just confused on 'zilla's mention of B-Body.
Is there an A body with 10" drums and BBP?

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1964 Dart GT

He means that the BBP a bodies use the same drums as b bodies.I believe all late a bodies (73-76) with BBP will be 10" drums. Someone will correct me if I am wrong.

Thanks all.I think I answered my own questions.

http://www.moparaction.com/tech/archive/disc-main.html

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1964 Dart GT

That is correct. They used B/E body brakes which have a wider offset than SBP A body brakes.

To use the 10" BBP brakes you have to get the housing and axles too. The BBP brakes will not bolt on to a SBP housing. (BBP flange is a 5 bolt pattern, SBP is 4 bolt) The BBP axles also have a bigger bearing on them and will not fit in an SBP housing either. Look under 73-76 A body disc brake cars.

I have a BBP 7.25" laying in my shop, minus brakes. Come and get it.

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Official Cookie and Mater Tormentor.